Study of the D⇄Sb (D = O, S) Transannular Interaction in Sb‐Monohalogenated Dibenzostibocines − An Experimental and Theoretical Study

In order to gain a greater insight in the nature of the D⇄Sb transannular interaction in dibenzostibocines, a series of D(C 6 H 4 S) 2 SbHal complexes (D = S; Hal = Cl 1 , Br 2 , I 3 ; D = O, Hal = Cl 4 ) has been synthesised. X‐ray structure determinations of complexes 1 − 4 reveal that the antimony atom is in a distorted ψ‐bipyramidal geometry, acting as an acceptor atom. The eight‐membered ring conformation in 1 , 2 and 4 can be described as a twist‐boat, while in 3 it is approaching C s symmetry. DFT calculations were carried out on 1 and 4 . Topological analysis of the electron density in 1 and 4 showed the presence of critical points in the D⇄Sb direction (D = O, S). The electron localisation function showed the presence of a lone pair located in an equatorial position on the antimony, and a lone pair of the donor along the D⇄Sb direction, confirming the presence of a dative bond in the system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)